docs: def defverb(self, s1, p1, s2, p2, s3, p3):
          """
          Set the verb plurals for s1, s2 and s3 to p1, p2 and p3 respectively.
  
          Where 1, 2 and 3 represent the 1st, 2nd and 3rd person forms of the verb.
  
          """
          self.checkpat(s1)
          self.checkpat(s2)
          self.checkpat(s3)
          self.checkpatplural(p1)
          self.checkpatplural(p2)
          self.checkpatplural(p3)
          self.pl_v_user_defined.extend((s1, p1, s2, p2, s3, p3))
          return 1